Well, I went ahead and put new plugs and wires in it earlier as well as the stock air box. Let's hope that does something. Nothing on top of it other than the stock rack.

Also, what would be the best brand and ratio of gears to buy? As well as new speedo gear? Lots of questions! Never had anything lifted. Just muscle cars and full size trucks...

 

http://go.jeep-xj.info/HowtoSpeedoGears.htm

Read. Look what a 15 second Google search did for me.

And plugs and wires aren't gunna do anything at all really as far as mileage. You have 33 inch tires on stock gears. That's the mileage you're going to get before you regear. Hate to be the bearer of bad news.

You could check for a cracked exhaust manifold. If it is, you could replace it and see maybe another mpg or two. Other than that, nothing but gearing is really going to make a difference

 

First, if you don't know if your speedometer is corrected you don't know what kind of mileage you are getting. Second, gas gauges are almost always off.

You need to drive at least 200 miles with an accurate speedometer and then fill your tank and divide the miles driven by the gallons of gas it takes to fill the tank, that is the only way to know your mileage. The I got X number of miles in half a tank doesn't tell you anything.

No, larger tires make it look like your mileage is worse, because the odometer shows less miles than you have really traveled not more miles.

 

It can't be off by that much

 

Yes it can be off by that much! Off the top of my head I would say about 16%, plus the OP stated that he drove 80-90 miles in 1/2 tank. Which was it 80 or 90? Did he use 10 gallons or did he only use 6 gallons? If the OP used 6 gallons because his gauge is screwed up and drove over 90 miles his mileage would be better than 15 mpg which for a lifted, larger size tired Cherokee wouldn't be that bad.

Fill the tank, drive 200 miles, fill the tank and divide the miles by the gas needed to fill the tank. That is the only way to know the mpgs!

 

It definitely can be off by that much

 

Is yours a standard or auto and what gears are you running. Also check the distance you drive with a stock car. Your odometer is off a little as well as your speed o

 

amd if your passing everyone doing 60 mph, something is seriously wrong!!

 

I just want to throw in that I have basically the same specs as you (4.0, AW4, 3.55s) and I've done EVERYTHING as far as routine maintenance to try and boost my MPGs (all filter and fluids, full tune up, o2 sensors, new cat, seafoam, etc etc.)

You're not going to see a noticeable improvement unless you regear, redo your entire exhaust, and remove anything affecting weight and aerodynamics (roof racks, heavy bumpers, etc)

 

Hahaha this is very true. That's what happens with me

 

At some point i will re gear. I honestly dont know how far off my speedo is. Dont really care! It needs some work but no big deal.

 

I normally hold it at about 45 in a 50 and everyone is always passing me

 

150-200 miles a gallon is pretty average. your lucky to get more

 

150-200 miles per gallon? Whats your secret?

Haha but seriously to the other poster if I could get more than 11mpg I would be happy- somethings up with my jeep though- I used to get 16mpg when I had 33s.

 

Keep saying things like that and I'm gonna keep boring you with math.

Stock tires (205/75-R15) have a diameter of 27.1 which yields a circumference of 85.16 inches.

33s have a diameter of... well, 33. Their circumference is 103.67 inches.

So, for every revolution of your 33s your Jeep travels 18.51 inches further than it does on the stock tires your speed-o gear assumes you have. "No big deal" you say. 18 and a half inches isn't that much, right? Over the course of one mile, that 18.5 inches adds up to 916 feet so over 200 miles you've actually traveled 35 miles more than your stock speed-o gear tells your odometer you've traveled.

...That will affect your fuel mileage calculations. Add to that the parasitic loss caused by having to accelerate the larger mass of your 33s, the increased rolling resistance, and the increased wind resistance and things look pretty grim.

Regear so that it's less work for your engine to get those tires going and less to keep them going, and change your speedo gear so that your odometer is showing the actual distance traveled. Those two things will improve your mileage by 20% or more.

Or go back to stock tires. I get around 16 mpg in daily city driving and 22+ on the highway.